Thermally Controlled Active Flow Control System

ABSTRACT

A method and apparatus are presented. An active flow control system comprises a flow control valve, a manifold, and a temperature control system. The flow control valve is configured to control a flow of air into the manifold. The manifold is operatively connected to a number of actuators. The temperature control system is configured to heat at least a portion of the flow of air.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of and claims the benefit of priorityto U.S. patent application Ser. No. 15/131,393, filed Apr. 18, 2016, theentire contents of which are incorporated herein by reference.

BACKGROUND INFORMATION 1. Field

The present disclosure relates generally to flow control and, inparticular, to an active flow control system. More particularly, thepresent disclosure relates to decreasing the input in a flow controlsystem on an aircraft.

2. Background

Flow control is an emerging technology which aims at enhancing theaerodynamic performance and efficiency of flight vehicles. A flowcontrol system includes a flow control actuator for supplying a gas flowover an aerodynamic structure. Flow control systems with fluidic devicesare effective and use an air supply as input. Energizing the airflowover an aerodynamic surface using small jets of air will increase theperformance and efficiency of the aerodynamic surface. The higher theflow control performance target, the higher the fluidic input for theflow control system. By increasing performance of the flow controlsystem, mass flow into the flow control system is also increased.

To provide higher fluidic input, greater system resources are used. Ifengine bleed is used, for example, engine size may be increased toprovide higher fluidic input. However, increasing engine size alsoincreases the weight of the engine, thus increasing the airplane grossweight.

Therefore, it would be desirable to have a method and apparatus thattake into account at least some of the issues discussed above, as wellas other possible issues.

SUMMARY

In one illustrative embodiment, an active flow control system comprisesa flow control valve, a manifold, and a temperature control system. Theflow control valve is configured to control a flow of air into themanifold. The manifold is operatively connected to a number ofactuators. The temperature control system is configured to heat at leasta portion of the flow of air.

In another illustrative embodiment, a method is provided. A flow of airis controlled into a manifold operatively connected to a number ofactuators of an active flow control system. At least a portion of theflow of air is heated using a temperature control system to form aheated portion. The heated portion is directed towards the number ofactuators.

In yet another illustrative embodiment, a method is provided. Activeflow control having a desired momentum is provided using an active flowcontrol system having a number of actuators. A mass flow through thenumber of actuators is decreased while maintaining the desired momentumfrom the number of actuators.

The features and functions can be achieved independently in variousembodiments of the present disclosure or may be combined in yet otherembodiments in which further details can be seen with reference to thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and features thereof, will best be understood by reference tothe following detailed description of an illustrative embodiment of thepresent disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of an aircraft in which an illustrativeembodiment may be implemented;

FIG. 2 is an illustration of a block diagram of an aircraft inaccordance with an illustrative embodiment;

FIG. 3 is an illustration of an active flow control system in accordancewith an illustrative embodiment;

FIG. 4 is an illustration of a cross-sectional view of actuators of anactive flow control system in accordance with an illustrativeembodiment;

FIG. 5 is an illustration of a cross-sectional view of actuators of anactive flow control system in accordance with an illustrativeembodiment;

FIG. 6 is an illustration of thermal profiles for an active flow controlsystem in accordance with an illustrative embodiment;

FIG. 7 is an illustration of the effect of heated air supply to anactuator in accordance with an illustrative embodiment;

FIG. 8 is an illustration of another active flow control system inaccordance with an illustrative embodiment;

FIG. 9 is an illustration of a cross-sectional view of actuators of anactive flow control system in accordance with an illustrativeembodiment;

FIG. 10 is an illustration of thermal profiles for an active flowcontrol system in accordance with an illustrative embodiment;

FIG. 11 is an illustration of thermal profiles for an active flowcontrol system in accordance with an illustrative embodiment;

FIG. 12 is an illustration of a flowchart of a process for providingactive flow control in accordance with an illustrative embodiment;

FIG. 13 is an illustration of a flowchart of a process for providingactive flow control in accordance with an illustrative embodiment;

FIG. 14 is a data processing system in the form of a block diagram inaccordance with an illustrative embodiment;

FIG. 15 is an illustration of an aircraft manufacturing and servicemethod in the form of a block diagram in accordance with an illustrativeembodiment; and

FIG. 16 is an illustration of an aircraft in the form of a block diagramin which an illustrative embodiment may be implemented.

DETAILED DESCRIPTION

The illustrative embodiments recognize and take into account one or moredifferent considerations. For example, the illustrative embodimentsrecognize and take into account that the mass flow rate and the momentumthrough an actuator are based on the thermodynamic properties of afluid. For example, the mass flow rate and momentum are influenced bythe pressure and the temperature of the fluid.

The illustrative embodiments recognize and take into account that acompressor or an auxiliary power unit may supply the fluid to anactuator array rather than an engine. However, a compressor or anauxiliary power unit may add weight to the aircraft. As a result, theillustrative embodiments recognize and take into account that using theleast amount of air flow for the system may be desirable regardless ofwhether the flow is supplied by an engine, a compressor, or an auxiliarypower unit.

Referring now to the figures and, in particular, with reference to FIG.1, an illustration of an aircraft is depicted in which an illustrativeembodiment may be implemented. In this illustrative example, aircraft100 has wing 102 and wing 104 attached to body 106. Aircraft 100includes engine 108 attached to wing 102 and engine 110 attached to wing104. Body 106 has tail section 112. Horizontal stabilizer 114,horizontal stabilizer 116, and vertical stabilizer 118 are attached totail section 112 of body 106.

Aircraft 100 is an example of an aircraft having an active flow controlsystem. For example, a thermally controlled active flow control systemmay enhance performance and efficiency of aerodynamic structures in atleast one of tail section 112, wing 102, or wing 104.

This illustration of aircraft 100 is provided for purposes ofillustrating one environment in which the different illustrativeembodiments may be implemented. The illustration of aircraft 100 in FIG.1 is not meant to imply architectural limitations as to the manner inwhich different illustrative embodiments may be implemented. Forexample, aircraft 100 is shown as a commercial passenger aircraft. Thedifferent illustrative embodiments may be applied to other types ofaircraft, such as a private passenger aircraft, a rotorcraft, or othersuitable types of aircraft.

Although the illustrative examples for an illustrative embodiment aredescribed with respect to an aircraft, an illustrative embodiment may beapplied to other types of platforms. The platform may be, for example, amobile platform, a stationary platform, a land-based structure, anaquatic-based structure, or a space-based structure. More specifically,the platform may be a surface ship, a tank, a personnel carrier, atrain, a spacecraft, a space station, a satellite, a submarine, anautomobile, a manufacturing facility, a building, or other suitableplatforms.

Turning now to FIG. 2, an illustration of a block diagram of an aircraftis depicted in accordance with an illustrative embodiment. Aircraft 200is an example of systems of aircraft 100 in FIG. 1 depicted in blockformat. Active flow control system 202 of FIG. 2 may be implemented inany desirable portion of aircraft 100. For example, active flow controlsystem 202 may be associated with tail section 112 of aircraft 100.

Active flow control system includes flow control valve 204 configured tocontrol flow 206 of air into manifold 208. Manifold 208 is operativelyconnected to number of actuators 210. Temperature control system 212 isconfigured to heat at least a portion of flow 206.

Auxiliary power unit 214 provides flow 206 having temperature 216 tomanifold 208 of active flow control system 202. Flow 206 is the input toactive flow control system 202. Temperature 216 may be any desirabletemperature. For example, temperature 216 may be within the range ofambient temperature to approximately 800 degrees Fahrenheit. The ambienttemperature is the temperature outside of aircraft 200. Flow 206 isintroduced into manifold 208. Manifold 208 directs flow 206 towardsactuator array 218 which includes number of actuators 210. Actuatorarray 218 directs jets of air outside of aircraft 200.

Temperature control system 212 increases the temperature of at least aportion of flow 206. By heating at least a portion of flow 206, massflow 220 through first actuator 222 of number of actuators 210 isreduced. By increasing the temperature of at least a portion of flow206, mass flow 220 through first actuator 222 is decreased withoutundesirably affecting momentum 224 provided by first actuator 222.

Temperature control system 212 may take different optional forms. In afirst illustrative example, temperature control system 212 redirects theportion of flow 206 from manifold 208 and then reintroduces the heatedportion back into manifold 208. In a second illustrative example,temperature control system 212 heats flow 206 as it travels through atleast one of a portion of manifold 208 or actuator array 218.

As used herein, the phrase “at least one of,” when used with a list ofitems, means different combinations of one or more of the listed itemsmay be used, and only one of each item in the list may be needed. Inother words, “at least one of” means any combination of items and numberof items may be used from the list, but not all of the items in the listare required. The item may be a particular object, thing, or a category.

For example, “at least one of item A, item B, or item C” may include,without limitation, item A, item A and item B, or item B. This examplealso may include item A, item B, and item C or item B and item C. Ofcourse, any combinations of these items may be present. In otherexamples, “at least one of” may be, for example, without limitation, twoof item A; one of item B; and ten of item C; four of item B and seven ofitem C; or other suitable combinations.

Using temperature control system 212, temperature at inlet 226 isgreater than temperature 216 of flow 206 entering manifold 208.Temperature of mass flow 220 through first actuator 222 decreases fromthe inlet of first actuator 222 to the outlet of first actuator 222.Thus, temperature at inlet 226 is greater than temperature at outlet228.

Surrounding structures 230 of aircraft 200 may be undesirably affectedby high temperatures. By temperature of mass flow 220 decreasing throughfirst actuator 222, surrounding structures 230 of aircraft 200 are notundesirably affected by the output of first actuator 222.

In a first example, temperature control system 212 includes flowproportioning valve 232, heater 234, and ductwork 236. Heater 234 isconfigured to heat at least a portion of flow 206 of air to form aheated portion. Flow proportioning valve 232 directs the at least aportion of flow 206 of air towards heater 234. Ductwork 236 extendsthrough a portion of manifold 208. Ductwork 236 directs the heatedportion towards number of actuators 210.

Ductwork 236 has any desirable sized and shaped cross-section. In someillustrative examples, ductwork 236 has more than one cross-section. Thenumber of cross-sections of ductwork 236 may be selected from square,rectangular, circular, oval-shaped, or any other desirable shape.

There is a space between ductwork 236 and manifold 208. The space isconfigured to insulate surrounding structures 230. By insulatingsurrounding structures 230, surrounding structures 230 may be protectedfrom undesirable amounts of heat.

In a second example, temperature control system 212 includes powersource 238, resistive heater strips 240, and insulation 242. Resistiveheater strips 240 are operatively connected to power source 238.Resistive heater strips 240 are positioned in a portion of manifold 208.In some illustrative examples, heater material is positioned within eachof number of actuators 210. The heater material may be substantially thesame material as resistive heater strips 240. Insulation 242 ispositioned between manifold 208 and surrounding structures 230.Insulation 242 protects surrounding structures 230 from undesirableamounts of heat.

Resistive heater strips 240 and other heater material positioned in atleast one of a portion of manifold 208 or number of actuators 210 heatsflow 206 of air as flow 206 passes through manifold 208 and actuatorarray 218. More specifically, air is heated as it travels past resistiveheater strips 240 and other heater material. In this illustrativeexample, resistive heater strips 240 and other heater material oftemperature control system 212 heats all of flow 206. By heating flow206, mass flow through actuator array 218, including mass flow 220through first actuator 222, is decreased.

Controller 244 of active flow control system 202 controls operation ofat least one of flow control valve 204 or temperature control system212. Controller 244 may be implemented using hardware, software,firmware, or a combination thereof. When software is used, theoperations performed by controller 244 may be implemented using, forexample, without limitation, program code configured to run on aprocessor unit, such as processor unit 1404 illustrated below in FIG.14. When firmware is used, the operations performed by controller 244may be implemented using, for example, without limitation, program codeand data and may be stored in persistent memory to run on the processorunit.

When hardware is employed, the hardware may include one or more circuitsthat operate to perform the operations performed by controller 244.Depending on the implementation, the hardware may take the form of acircuit system, an integrated circuit, an application specificintegrated circuit (ASIC), a programmable logic device, or some othersuitable type of hardware device configured to perform any number ofoperations.

A programmable logic device may be configured to perform certainoperations. The device may be permanently configured to perform theseoperations or may be reconfigurable. A programmable logic device maytake the form of, for example, without limitation, a programmable logicarray, a programmable array logic, a field programmable logic array, afield programmable gate array, or some other type of programmablehardware device.

In some illustrative examples, the operations and/or processes performedby controller 244 may be performed using organic components integratedwith inorganic components. In some cases, the operations and/orprocesses may be performed entirely by organic components, excluding ahuman being. As one illustrative example, circuits in organicsemiconductors may be used to perform these operations and/or processes.

Controller 244 may be implemented within a computer system. The computersystem may be comprised of one or more computers. When more than onecomputer is present in the computer system, these computers may be incommunication with each other.

The illustration of aircraft 200 in FIG. 2 is not meant to implyphysical or architectural limitations to the manner in which anillustrative embodiment may be implemented. Other components in additionto or in place of the ones illustrated may be used. Some components maybe unnecessary. Also, the blocks are presented to illustrate somefunctional components. One or more of these blocks may be combined,divided, or combined and divided into different blocks when implementedin an illustrative embodiment.

For example, rather than auxiliary power unit 214, active flow controlsystem 202 may include a compressor. As another example, rather thanauxiliary power unit 214, active flow control system 202 may includebleed from an engine of aircraft 200.

Turning now to FIG. 3, an illustration of an active flow control systemis depicted in accordance with an illustrative embodiment. Active flowcontrol system 300 is a diagram depiction of active flow control system202 of FIG. 2. Active flow control system 300 may be used to provideflow control to aircraft 100 of FIG. 1.

Active flow control system 300 includes auxiliary power unit 302, flowcontrol valve 304, manifold 306, temperature control system 308, andactuator array 310. Auxiliary power unit 302 provides a flow of air tomanifold 306.

As depicted, temperature control system 308 heats a portion of the flowof air provided by auxiliary power unit 302. Temperature control system308 includes flow proportioning valve 312, heater 314, and ductwork 316.Flow proportioning valve 312 directs a portion of the flow of airtowards heater 314. Heater 314 is configured to heat the portion of theflow of air received from flow proportioning valve 312 to form a heatedportion.

The heated portion travels through ductwork 316 towards actuator array310. Ductwork 316 extends through portion 318 of manifold 306. Ductwork316 directs the heated portion towards first actuator 320, secondactuator 322, and third actuator 324 of actuator array 310. Althoughactuator array 310 is depicted as having three actuators, actuator array310 may have any desirable number of actuators. In one illustrativeexample, actuator array 310 has more than three actuators. In anotherillustrative example, actuator array 310 has fewer than three actuators.

The heated portion will mix with the remainder of the flow of air withinactuator array 310. By heating the portion of the flow of air, momentumprovided by actuator array 310 remains substantially the same while massflow through actuator array 310 is decreased.

Turning now to FIG. 4, an illustration of a cross-sectional view ofactuators of an active flow control system is depicted in accordancewith an illustrative embodiment. View 400 is an isometriccross-sectional view of one physical implementation of actuator array310 of FIG. 3. Cross-sections of first actuator 320, second actuator322, and third actuator 324 of actuator array 310 are visible in view400. In this implementation, ductwork 316 has a rectangularcross-section. Ductwork 316 extends through the portion of manifold 306supplying a heated portion of air to first actuator 320, second actuator322, and third actuator 324.

The heated portion supplied by ductwork 316 mixes with the remainder ofthe flow traveling in the space between ductwork 316 and manifold 306.The heated portion and the remainder of the flow enter first actuator320, second actuator 322, and third actuator 324 of actuator array 310.

The temperature of air entering third actuator 324 at inlet 402 isgreater than the temperature of air exiting third actuator 324 at outlet404. The temperature of air entering second actuator 322 at inlet 406 isgreater than the temperature of air exiting second actuator 322 atoutlet 408. The temperature of air entering first actuator 320 at inlet410 is greater than the temperature of air exiting first actuator 320 atoutlet 412.

Turning now to FIG. 5, an illustration of a cross-sectional view ofactuators of an active flow control system is depicted in accordancewith an illustrative embodiment. View 500 is an isometriccross-sectional view of one physical implementation of actuator array310 of FIG. 3. Cross-sections of first actuator 320, second actuator322, and third actuator 324 of actuator array 310 are visible in view500. In this implementation, ductwork 316 has a circular cross-sectionand an oval cross-section. Ductwork 316 extends through the portion ofmanifold 306 supplying heated portion of air to first actuator 320,second actuator 322, and third actuator 324.

The heated portion supplied by ductwork 316 mixes with the remainder offlow traveling in the space between ductwork 316 and manifold 306. Theheated portion and the remainder of the flow enter first actuator 320,second actuator 322, and third actuator 324 of actuator array 310.

The temperature of air entering third actuator 324 at inlet 502 isgreater than the temperature of air exiting third actuator 324 at outlet504. The temperature of air entering second actuator 322 at inlet 506 isgreater than the temperature of air exiting second actuator 322 atoutlet 508. The temperature of air entering first actuator 320 at inlet510 is greater than the temperature of air exiting first actuator 320 atoutlet 512.

Turning now to FIG. 6, an illustration of thermal profiles for an activeflow control system is depicted in accordance with an illustrativeembodiment. Thermal data 600 is an example of thermal data from anactuator of actuator array 310 of FIG. 3. Thermal data 600 may be anexample of thermal data from an actuator of actuator array 218 of FIG.2.

Thermal data 600 includes x-axis 602 and y-axis 604. X-axis 602 is adistance measurement. Y-axis 604 is a ratio of the temperature of airentering an inlet over the ambient temperature. Line 606 represents thetemperature of air along the center line of an actuator with atemperature equal to the ambient level at the inlet. The ambienttemperature is sometimes referred to as the conventional temperature.Line 608 represents the temperature of air along the centerline of anactuator with twice the conventional air temperature at the inlet. Line610 represents the temperature of air along the centerline of anactuator with four times the conventional air temperature at the inlet.

As depicted, the temperature of air exiting the actuator in line 610 isonly twice the temperature of the conventional air flow input. Thetemperature of air exiting the actuator in line 608 is less than 1.5times the temperature of the conventional air flow input.

Each of line 606, line 608, and line 610 converge outside of theactuator in less than the length of the actuator. As depicted, each ofline 606, line 608, and line 610 converge outside of the actuator inabout one fourth the length of the actuator.

Due to the relatively rapid convergence of line 606, line 608, and line610, surrounding structures may not be undesirably affected. Morespecifically, the output of line 608 or line 610 may not undesirablyaffect surrounding structures.

Turning now to FIG. 7, an illustration of the effect of heated airsupply to an actuator is depicted in accordance with an illustrativeembodiment. FIG. 7 depicts flow properties in a slice that cuts throughthe center of the actuator. Actuator characteristics 700 are an exampleof characteristics of an actuator of actuator array 310 of FIG. 3.Actuator characteristics 700 may be an example of characteristics of anactuator of actuator array 218 of FIG. 2.

Characteristics 700 include mass flow 702, momentum 704, and temperature706. Mass flow 702 is the mass flow entering an inlet of the actuatornormalized by the ambient conditions. Momentum 704 is the momentumentering an inlet of the actuator normalized by the ambient conditions.Temperature 706 is the temperature entering an inlet of the actuatornormalized by the ambient temperature.

First column 708 depicts characteristics for an inlet temperature ofambient temperature. The ambient temperature is sometimes referred to asthe conventional temperature. Second column 710 depicts characteristicsfor an inlet temperature of twice the conventional temperature at theinlet. Third column 712 depicts characteristics for an inlet temperatureof four times the conventional temperature at the inlet.

As can be seen in characteristics 700, mass flow 702 decreases withincreased temperature at the inlet. For example, mass flow 702 isgreater for first column 708 than either of second column 710 or thirdcolumn 712. Further, mass flow 702 for third column 712 is less thansecond column 710.

Although mass flow 702 decreases with increased temperature, momentum704 stays substantially the same with increased temperature. Forexample, momentum 704 for first column 708, second column 710, and thirdcolumn 712 appear substantially the same.

Additionally, temperature 706 of air exiting the actuator for each offirst column 708, second column 710, and third column 712 will notundesirably affect surrounding structures. As shown, temperature 706 ofair exiting the actuator for third column 712 is greater than firstcolumn 708 and second column 710, but quickly dissipates.

As can be seen in FIG. 7, having a higher temperature of air travelingthrough an actuator can decrease the mass flow through the actuatorwithout undesirably decreasing momentum. Characteristics 700 of FIG. 7are for an active flow control system having a heater and ductwork.However, decreased mass flow and substantially the same momentum alsoresults from other embodiments of a temperature control system, such asthe temperature control system in FIGS. 8 and 9 below.

Turning now to FIG. 8, an illustration of another active flow controlsystem is depicted in accordance with an illustrative embodiment. Activeflow control system 800 is a diagram depiction of active flow controlsystem 202 of FIG. 2. Active flow control system 800 may be used toprovide flow control to aircraft 100 of FIG. 1.

Active flow control system 800 includes auxiliary power unit 802, flowcontrol valve 804, manifold 806, temperature control system 808, andactuator array 810. Auxiliary power unit 802 provides a flow of air tomanifold 806.

As depicted, temperature control system 808 heats the air provided byauxiliary power unit 802. Temperature control system 808 includes powersource 812, resistive heater strips 814, and ductwork 816. Power source812 provides power to resistive heater strips 814. Resistive heaterstrips 814 and heating material positioned within at least one ofmanifold 806 or actuator array 810 heat the air as it travels past theresistive heater strips 814 and other heating material. In someexamples, ductwork 816 takes the form of heating material.

In some illustrative examples, heating material may only be presentwithin actuator array 810. As depicted, actuator array 810 includesfirst actuator 818, second actuator 820, and third actuator 822.

Although not visible in active flow control system 800, insulation maybe present between ductwork 816 and surrounding structures. Further,insulation may be present between actuator array 810 and surroundingstructures.

Turning now to FIG. 9, an illustration of a cross-sectional view ofactuators of an active flow control system is depicted in accordancewith an illustrative embodiment. View 900 is an isometriccross-sectional view of one physical implementation of actuator array810. Cross-sections of first actuator 818, second actuator 820, andthird actuator 822 of actuator array 810 are visible in view 900.Resistive heater strips 814 are clearly seen in view 900.

As depicted, heater material lines the internal surfaces of firstactuator 818, second actuator 820, and third actuator 822 of actuatorarray 810. By having heater material blanketing all surfaces of anactuator, maximum heat transfer to the fluid within the actuator occurs.For example, vertical walls 824 of first actuator 818, vertical walls826 of second actuator 820 and vertical walls 828 of third actuator 822are covered with heater material. Further, heater material covers bottomwall 830 of first actuator 818, bottom wall 832 of second actuator 820and bottom wall 834 of third actuator 822. Although the top walls offirst actuator 818, second actuator 820, and third actuator 822 are notdepicted, heater material may also cover the tops walls.

Although this illustrative example includes heater material lining allinternal surfaces of each of first actuator 818, second actuator 820,and third actuator 822, in some other examples heater material is onlypresent on a portion of an internal surface of at least one of firstactuator 818, second actuator 820, or third actuator 822.

Turning now to FIG. 10, an illustration of thermal profiles for anactive flow control system is depicted in accordance with anillustrative embodiment. Thermal data 1000 is an example of thermal datafrom an actuator of actuator array 810 of FIG. 8. Thermal data 1000 maybe an example of thermal data from an actuator of actuator array 218 ofFIG. 2.

Thermal data 1000 includes x-axis 1002 and y-axis 1004. X-axis 1002 is adistance measurement. Y-axis 1004 is a ratio of the temperature of airentering an inlet over the ambient temperature. The ambient temperatureis the temperature outside of the aircraft. The ambient temperature issometimes referred to as the conventional temperature. Line 1006represents the temperature of air along the centerline of an actuatorwith a temperature equal to the ambient air temperature at the inlet.Line 1008 represents the temperature of air along the centerline of anactuator with the conventional air temperature at the inlet, andactuator walls heated to four times the conventional air temperature.Line 1010 represents the temperature of air along the centerline of anactuator with four times the conventional air temperature at the inlet.

The shape of the actuator in FIG. 6 is the same shape of the actuator inFIG. 10. Accordingly, line 1006 is the same as line 606 of FIG. 6.Likewise, line 1010 is the same as line 610 of FIG. 6.

As depicted, the temperature of air exiting the actuator in line 1010 isonly twice the temperature of the conventional air flow input. Thetemperature of air exiting the actuator in line 1008 is about the sameas the conventional air temperature. More specifically, the temperatureof air exiting the actuator in line 1008 is less than 1.2 times thetemperature of the conventional air flow input.

As depicted, line 1008 converges to about the conventional airtemperature in a greater distance than line 1010. Line 1008 does notexceed 1.2 times the temperature of the conventional air flow input,however, line 1008 reaches nearly the conventional air flow input inabout the length of the actuator.

Due to the relatively low temperature of air exiting the actuator inline 1008, surrounding structures may not be undesirably affected. Morespecifically, the output of line 1008 may not undesirably affectsurrounding structures.

Turning now to FIG. 11, an illustration of thermal profiles for anactive flow control system is depicted in accordance with anillustrative embodiment. Thermal data 1100 may be an example of thermaldata from an actuator of actuator array 218 of FIG. 2. Thermal data 1100is an example of thermal data from an actuator having a different designthan actuators of actuator array 310 of FIG. 3 or actuator array 810 ofFIG. 8. Thermal data 1100 is an example of thermal data from an actuatorassociated with a temperature control system similar to temperaturecontrol system 308 of FIG. 3.

Thermal data 1100 for actuator cross-section 1101 includes x-axis 1102and y-axis 1104. X-axis 1102 is a distance measurement. Y-axis 1104 is aratio of the temperature of air entering an inlet over the conventionaltemperature. Line 1106 represents the temperature of air along thecenterline of an actuator with the ambient air temperature at the inlet.The ambient temperature is sometimes referred to as the conventionaltemperature. Line 1108 represents the temperature of air along thecenterline of an actuator with twice the conventional air temperature atthe inlet. Line 1110 represents the temperature of air along thecenterline of an actuator with four times the conventional airtemperature at the inlet.

As depicted, the temperature of air exiting the actuator in line 1110 isonly twice the temperature of the conventional air flow input. Thetemperature of air exiting the actuator in line 1108 is less than 1.5times the temperature of the conventional air flow input.

Each of line 1106, line 1108, and line 1110 converge outside of theactuator in about the length of the actuator. Due to the relativelyrapid convergence of line 1106, line 1108, and line 1110, surroundingstructures may not be undesirably affected. More specifically, theoutput of line 1108 or line 1110 may not undesirably affect surroundingstructures beyond a distance of approximately half the actuator length.In some illustrative examples, insulation may additionally be placedaround any surrounding structures to protect the surrounding structuresfrom higher temperatures.

Turning now to FIG. 12, an illustration of a flowchart of a process forproviding active flow control is depicted in accordance with anillustrative embodiment. Process 1200 is a process of providing activeflow control using active flow control system 202 of FIG. 2. Process1200 may provide active flow control to aircraft 100 of FIG. 1. Process1200 may be implemented using active flow control system 300 of FIG. 3.Process 1200 may be implemented using active flow control system 800 ofFIG. 8.

Process 1200 controls a flow of air into a manifold operativelyconnected to a number of actuators of an active flow control system(operation 1202). Process 1200 heats at least a portion of the flow ofair using a temperature control system to form a heated portion(operation 1204). In some examples, heating the at least a portion ofthe flow of air using the temperature control system comprises routingthe at least a portion towards a heater of the temperature controlsystem using a proportioning valve of the temperature control system. Inother examples, heating the at least a portion of the flow of air usingthe temperature control system comprises: providing power to resistiveheater strips positioned in a portion of the manifold. In some examples,heating the at least a portion of the flow of air using the temperaturecontrols system comprises: providing power to resistive heater stripspositioned in the number of actuators. Heating the at least a portion ofthe flow of air using a temperature control system to form a heatedportion decreases a mass flow through the number of actuators.

Process 1200 directs the heated portion towards the number of actuators(operation 1206). Afterwards, the process terminates. In someillustrative examples, directing the heated portion towards the numberof actuators comprises: routing the heated portion using ductwork of thetemperature control system, wherein the ductwork extends through aportion of the manifold, and wherein the ductwork directs the heatedportion towards the number of actuators. In some illustrative examples,directing the heated portion towards the number of actuators furthercomprises: insulating surrounding structures by directing a remainder ofthe flow through the manifold around the ductwork.

Turning now to FIG. 13, an illustration of a flowchart of a process forproviding active flow control is depicted in accordance with anillustrative embodiment. Process 1300 is a process of providing activeflow control using active flow control system 202 of FIG. 2. Process1300 may provide active flow control to aircraft 100 of FIG. 1. Process1300 may be implemented using active flow control system 300 of FIG. 3.Process 1300 may be implemented using active flow control system 800 ofFIG. 8.

Process 1300 provides active flow control having a desired momentumusing an active flow control system having a number of actuators(operation 1302). Process 1300 decreases a mass flow through the numberof actuators while maintaining the desired momentum from the number ofactuators (operation 1304). Decreasing the mass flow comprises heatingat least a portion of a flow of air in the active flow control systemusing a temperature control system. In some illustrative examples,heating the at least a portion of the flow of air comprises: routing theat least a portion of the flow of air towards a heater of thetemperature control system using a proportioning valve of thetemperature control system. In other illustrative examples, heating theat least a portion of the flow of air comprises: providing power toresistive heater strips positioned in a portion of a manifold of theactive flow control system.

The flowcharts and block diagrams in the different depicted embodimentsillustrate the architecture, functionality, and operation of somepossible implementations of apparatus and methods in an illustrativeembodiment. In this regard, each block in the flowcharts or blockdiagrams may represent a module, a segment, a function, and/or a portionof an operation or step.

In some alternative implementations of an illustrative embodiment, thefunction or functions noted in the blocks may occur out of the ordernoted in the figures. For example, in some cases, two blocks shown insuccession may be executed substantially concurrently, or the blocks maysometimes be performed in the reverse order, depending upon thefunctionality involved. Also, other blocks may be added in addition tothe illustrated blocks in a flowchart or block diagram.

Turning now to FIG. 14, an illustration of a data processing system isdepicted in the form of a block diagram in accordance with anillustrative embodiment. Data processing system 1400 may be used toimplement controller 244 in FIG. 2. As depicted, data processing system1400 includes communications framework 1402, which providescommunications between processor unit 1404, storage devices 1406,communications unit 1408, input/output unit 1410, and display 1412. Insome cases, communications framework 1402 may be implemented as a bussystem.

Processor unit 1404 is configured to execute instructions for softwareto perform a number of operations. Processor unit 1404 may comprise anumber of processors, a multi-processor core, and/or some other type ofprocessor, depending on the implementation. In some cases, processorunit 1404 may take the form of a hardware unit, such as a circuitsystem, an application specific integrated circuit (ASIC), aprogrammable logic device, or some other suitable type of hardware unit.

Instructions for the operating system, applications, and/or programs runby processor unit 1404 may be located in storage devices 1406. Storagedevices 1406 may be in communication with processor unit 1404 throughcommunications framework 1402. As used herein, a storage device, alsoreferred to as a computer-readable storage device, is any piece ofhardware capable of storing information on a temporary and/or permanentbasis. This information may include, but is not limited to, data,program code, and/or other information.

Memory 1414 and persistent storage 1416 are examples of storage devices1406. Memory 1414 may take the form of, for example, a random accessmemory or some type of volatile or non-volatile storage device.Persistent storage 1416 may comprise any number of components ordevices. For example, persistent storage 1416 may comprise a hard drive,a flash memory, a rewritable optical disk, a rewritable magnetic tape,or some combination of the above. The media used by persistent storage1416 may or may not be removable.

Communications unit 1408 allows data processing system 1400 tocommunicate with other data processing systems and/or devices.Communications unit 1408 may provide communications using physicaland/or wireless communications links.

Input/output unit 1410 allows input to be received from and output to besent to other devices connected to data processing system 1400. Forexample, input/output unit 1410 may allow user input to be receivedthrough a keyboard, a mouse, and/or some other type of input device. Asanother example, input/output unit 1410 may allow output to be sent to aprinter connected to data processing system 1400.

Display 1412 is configured to display information to a user. Display1412 may comprise, for example, without limitation, a monitor, a touchscreen, a laser display, a holographic display, a virtual displaydevice, and/or some other type of display device.

In this illustrative example, the processes of the differentillustrative embodiments may be performed by processor unit 1404 usingcomputer-implemented instructions. These instructions may be referred toas program code, computer usable program code, or computer-readableprogram code and may be read and executed by one or more processors inprocessor unit 1404.

In these examples, program code 1418 is located in a functional form oncomputer-readable media 1420, which is selectively removable, and may beloaded onto or transferred to data processing system 1400 for executionby processor unit 1404. Program code 1418 and computer-readable media1420 together form computer program product 1422. In this illustrativeexample, computer-readable media 1420 may be computer-readable storagemedia 1424 or computer-readable signal media 1426.

Computer-readable storage media 1424 is a physical or tangible storagedevice used to store program code 1418, rather than a medium thatpropagates or transmits program code 1418. Computer-readable storagemedia 1424 may be, for example, without limitation, an optical ormagnetic disk or a persistent storage device that is connected to dataprocessing system 1400.

Alternatively, program code 1418 may be transferred to data processingsystem 1400 using computer-readable signal media 1426. Computer-readablesignal media 1426 may be, for example, a propagated data signalcontaining program code 1418. This data signal may be an electromagneticsignal, an optical signal, and/or some other type of signal that can betransmitted over physical and/or wireless communications links.

Illustrative embodiments of the disclosure may be described in thecontext of aircraft manufacturing and service method 1500 as shown inFIG. 15 and aircraft 1600 as shown in FIG. 16. Turning first to FIG. 15,an illustration of an aircraft manufacturing and service method isdepicted in accordance with an illustrative embodiment. Duringpre-production, aircraft manufacturing and service method 1500 mayinclude specification and design 1502 of aircraft 1600 in FIG. 16 andmaterial procurement 1504.

During production, component and subassembly manufacturing 1506 andsystem integration 1508 of aircraft 1600 takes place. Thereafter,aircraft 1600 may go through certification and delivery 1510 in order tobe placed in service 1512. While in service 1512 by a customer, aircraft1600 is scheduled for routine maintenance and service 1514, which mayinclude modification, reconfiguration, refurbishment, and othermaintenance or service.

Each of the processes of aircraft manufacturing and service method 1500may be performed or carried out by a system integrator, a third party,and/or an operator. In these examples, the operator may be a customer.For the purposes of this description, a system integrator may include,without limitation, any number of aircraft manufacturers andmajor-system subcontractors; a third party may include, withoutlimitation, any number of vendors, subcontractors, and suppliers; and anoperator may be an airline, a leasing company, a military entity, aservice organization, and so on.

With reference now to FIG. 16, an illustration of an aircraft isdepicted in which an illustrative embodiment may be implemented. In thisexample, aircraft 1600 is produced by aircraft manufacturing and servicemethod 1500 in FIG. 15 and may include airframe 1602 with plurality ofsystems 1604 and interior 1606. Examples of systems 1604 include one ormore of propulsion system 1608, electrical system 1610, hydraulic system1612, and environmental system 1614. Any number of other systems may beincluded. Although an aerospace example is shown, different illustrativeembodiments may be applied to other industries, such as the automotiveindustry.

Apparatuses and methods embodied herein may be employed during at leastone of the stages of aircraft manufacturing and service method 1500.

One or more illustrative embodiments may be used during component andsubassembly manufacturing 1506 of FIG. 15. For example, active flowcontrol system 202 in FIG. 2 may be created during component andsubassembly manufacturing 1506. Active flow control system 202 enhancesaerodynamic performance of aircraft 1600 during in service 1512 of FIG.15. Further, portions of active flow control system 202, such astemperature control system 212 of FIG. 2, may be replaced or servicedduring maintenance and service 1514 of FIG. 15.

The illustrative embodiments provide a method and apparatus for activeflow control. The active flow control system includes a temperaturecontrol system. The temperature control system heats at least a portionof a flow of air within the active flow control system. In someillustrative examples, the temperature control system may heat the atleast a portion of the flow of air using a heater. In other illustrativeexamples, the temperature control system may heat the flow of air usinga power source and resistive heater strips.

The mass flow rate and the momentum through the actuator are based onthe thermodynamic properties of the fluid. The mass flow rate of thefluid is proportional to temperature. The momentum of the fluid isinvariable to the temperature. As a result, higher air supplytemperature results in reduced mass flow. Because the flow controleffect is a function of the momentum, the net impact of increased supplytemperature is reduced mass flow with no degradation in flow controlperformance. Increasing the fluid temperature is applicable to any flowcontrol technique employing ejection jets. Thus, increasing the fluidtemperature may be applied to constant blowing, sweeping jets, pulsedjets, or traverse actuation.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different features as compared to otherillustrative embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. An active flow control system comprising: a flowcontrol valve configured to control a flow of air into a manifold; themanifold operatively connected to a number of actuators; and atemperature control system configured to heat at least a portion of theflow of air, the temperature control system comprising a power sourceand resistive heater strips operatively connected to the power source,wherein the resistive heater strips are positioned in a portion of themanifold.
 2. The active flow control system of claim 1, wherein thetemperature control system further comprises heater material within eachof the number of actuators.
 3. The active flow control system of claim 1further comprising: insulation between the manifold and surroundingstructures.
 4. The active flow control system of claim 1, wherein thetemperature control system comprises: a heater configured to heat atleast the portion of the flow of air to form a heated portion.
 5. Theactive flow control system of claim 4, wherein the temperature controlsystem further comprises: a proportioning valve to direct the at leastthe portion of the flow of air towards the heater.
 6. The active flowcontrol system of claim 4, wherein the temperature control systemfurther comprises: ductwork extending through a portion of the manifold,wherein the ductwork directs the heated portion towards the number ofactuators.
 7. The active flow control system of claim 6, wherein thetemperature control system further comprises: a space between theductwork and the manifold configured to insulate surrounding structures.8. A method comprising: controlling a flow of air into a manifoldoperatively connected to a number of actuators of an active flow controlsystem; and heating at least a portion of the flow of air using atemperature control system to form a heated portion; and directing theheated portion towards the number of actuators; wherein heating the atleast the portion of the flow of air using the temperature controlsystem comprises providing power to resistive heater strips.
 9. Themethod of claim 8, wherein heating the at least the portion of the flowof air using the temperature controls system comprises: providing powerto resistive heater strips positioned in the number of actuators. 10.The method of claim 8, wherein heating the at least the portion of theflow of air using the temperature control system comprises: routing theat least the portion of the flow of air towards a heater of thetemperature control system using a proportioning valve of thetemperature control system.
 11. The method of claim 8, wherein directingthe heated portion towards the number of actuators comprises: routingthe heated portion using ductwork of the temperature control system,wherein the ductwork extends through a portion of the manifold, andwherein the ductwork directs the heated portion towards the number ofactuators.
 12. The method of claim 8, wherein directing the heatedportion towards the number of actuators further comprises: insulatingsurrounding structures by directing a remainder of the flow through themanifold around the ductwork.
 13. The method of claim 8, wherein heatingthe at least the portion of the flow of air using the temperaturecontrol system comprises: providing power to the resistive heater stripspositioned in a portion of the manifold.
 14. The method of claim 8,wherein heating the at least the portion of the flow of air using thetemperature controls system comprises: providing power to the resistiveheater strips positioned in the number of actuators.
 15. The method ofclaim 8, wherein heating the at least the portion of the flow of airusing the temperature control system to form the heated portiondecreases a mass flow through the number of actuators.
 16. A methodcomprising: providing active flow control having a desired momentumusing an active flow control system having a number of actuators; anddecreasing a mass flow through the number of actuators while maintainingthe desired momentum from the number of actuators.
 17. The method ofclaim 16, wherein the heating the at least the portion of the flow ofair comprises providing power to resistive heater strips positioned in aportion of a manifold of the active flow control system.
 18. The methodof claim 16, wherein decreasing the mass flow comprises: heating atleast a portion of a flow of air in the active flow control system usinga temperature control system.
 19. The method of claim 16, wherein theheating of the at least the portion of the flow of air comprises:routing the at least the portion of the flow of air towards a heater ofthe temperature control system using a proportioning valve of thetemperature control system.
 20. The method of claim 16, wherein theheating the at least the portion of the flow of air comprises: providingpower to resistive heater strips positioned in a portion of a manifoldof the active flow control system.